Symptom 1: No action on bucket and boom
Cause Analysis:
1) The failure of the hydraulic pump can be determined by measuring the outlet pressure of the pump. Possible reasons are: the pump shaft is broken or damaged, the rotation is ineffective or stuck, the bearing is rusted or stuck, the leakage is serious, and the floating side plate is severely injured or frayed.
2) The filter is clogged with noise.
3) The suction pipe is broken or loosely connected to the pump pipe joint.
4) Too little oil in the tank.
5) The fuel tank vent is blocked.
6) The main relief valve in the multi-way valve is damaged.
Remedy: check the hydraulic pump, find out the reason, and troubleshoot the hydraulic pump; clean or replace the filter screen: check the pipeline, joints, tank vent and main relief valve to eliminate the fault.
Symptom 2: weak boom lifting
The direct cause of the boom lifting weakness is insufficient pressure in the rodless cavity of the boom hydraulic cylinder. The main reasons are as follows: 1) The leak in the hydraulic pump is serious or the filter is clogged, resulting in insufficient oil delivery from the hydraulic pump. 2) Serious internal and external leakage of the hydraulic system.
The causes of internal leakage are: the total safety valve pressure of the multi-way directional valve is too low, or the main valve spool is stuck in the open position by the dirt (the main valve spool spring of the pilot valve is soft and easy to be dirty) Stuck); in the multi-way valve, the boom reversing valve is stuck at the drain position, the gap between the valve core and the valve body hole is too large or the check valve in the valve is not tight; the seal ring on the boom cylinder piston is damaged or Severe wear; Boom or strain of the boom cylinder; Excessive clearance between the valve plug of the flow control valve and the valve body hole; Excessive oil temperature.
Method of exclusion:
1) Check the filter, if it is blocked, clean or replace it; check the cause of the high oil temperature and eliminate it; if the oil is bad, replace it.
2) Check if the main safety valve is stuck. If it is stuck, just disassemble and clean the main valve spool to make it move freely. If the fault cannot be ruled out, operate the multi-way reversing valve, rotate the adjusting nut of the total safety valve, and observe the system pressure response. If the pressure can be adjusted to the specified value, the fault is basically eliminated.
3) Check whether the sealing ring of the hydraulic cylinder piston has lost the sealing effect: Take the boom cylinder to the bottom, and then remove the high-pressure hose from the outlet joint of the rodless cavity. At this time, the piston rod has reached the bottom and cannot be moved, so the pressure continues to increase. Then observe whether there is oil flowing out of the oil outlet. If only a small amount of oil flows out, it means that the seal ring has not failed. If there is a large oil flow (greater than 30mL / min), it means that the seal ring has failed and should be replaced.
4) According to the use of the multi-way valve, it can be analyzed whether the gap between the valve core and the valve body hole is too large. The normal clearance is 0.01mm, and the limit value is 0.04mm during repair. Remove and wash the slide valve to eliminate jamming.
5) Check the gap between the flow control valve spool and the valve body hole. The normal value is 0.015 to 0.025mm, and the maximum does not exceed 0.04mm. If the gap is too large, the valve should be replaced. Check the tightness of the check valve in the valve. If the seal is not good, you can grind the valve seat and replace the valve core. Inspect the spring and replace it if it is deformed, softened, or broken.
6) If the above possible causes are eliminated and the fault still exists, the hydraulic pump must be disassembled and inspected. For CBG gear pumps commonly used in this machine, the main check is the end face clearance of the pump, and the second is the check of the meshing clearance between the two gears and the radial clearance between the gear and the casing. If the clearance is too large, it means that the leakage is too large to produce enough pressure oil, and the main pump should be replaced at this time. The two end faces of the gear pump are sealed by two steel side plates coated with copper alloy. If the copper alloy on the side plates falls off or is seriously worn, the hydraulic pump cannot deliver sufficient pressure oil. The hydraulic pump should also be replaced at this time. Sick fried
7) If the boom is unable to lift and the bucket is retracted normally, the hydraulic pump, filter, flow distribution valve, total safety valve and oil temperature can be normal. Just verify and troubleshoot other issues.
Symptom 3: weak bucket retraction
Cause Analysis:
1) The main pump fails and the filter is blocked, resulting in insufficient oil delivery and insufficient pressure of the hydraulic pump.
2) The total safety valve is malfunctioning. The main valve spool is stuck or tightly sealed or the pressure is too low.
3) The flow control valve has failed. The gap is too large, and the check valve in the valve is not tight.
4) The valve of the bucket reversing valve and the valve body hole are too large for the hospital, they are stuck in the drain position, and the return spring is invalid.
5) Double-acting safety valve fails. The main valve spool is stuck or tightly sealed.
6) The seal ring of the bucket hydraulic cylinder is damaged, severely worn, and the cylinder tube is strained.
Method of exclusion:
1) Check whether the boom lifting is strong. If the boom lifting is normal, the hydraulic pump, filter, flow control valve, general safety valve and oil temperature are normal. Otherwise, troubleshoot according to the method described in Symptom 2.
2) Check the gap between the valve of the bucket reversing valve and the hole of the valve body. The limit gap is within 0.04mm. Clean the slide valve for repair or replacement of parts.
3) Disassemble and inspect the tightness and flexibility between the valve core and the valve seat of the double-acting safety valve, and between the valve core and the valve seat of the check valve, and clean the valve body and the valve core.
4) Remove the bucket hydraulic cylinder. It can be carried out according to the inspection method of the boom hydraulic cylinder described in the symptom 2.
Symptom 4: The settlement of the boom hydraulic cylinder is too large (falling off the boom)
Lift the full-load bucket and the multi-way valve is in the neutral position. At this time, the sinking distance of the piston rod of the boom hydraulic cylinder is the settlement amount. This machine requires that when the bucket is fully loaded and raised to the highest position for 30 minutes, the sinking is not more than 10mm. Excessive settlement will not only affect productivity, but also affect the accuracy of work equipment operations, and sometimes even accidents will occur.
Causes of boom hydraulic cylinder settlement:
1) The spool of the multi-way directional valve is not in the neutral position, and the oil circuit cannot be closed, causing the boom to fall off.
2) The gap between the spool of the multi-way directional valve and the valve body hole is too large, the seal is damaged, and the internal leakage is large.
3) The piston seal of the boom hydraulic cylinder fails, the piston becomes loose, and the cylinder tube is damaged.
Exclusion method: check the reason that the multi-way directional valve cannot reach the neutral position and remove it; check the gap between the multi-way directional valve and the valve body hole to ensure that the gap is within the repair limit of 0.04mm, replace the seal; replace the boom hydraulic Cylinder piston sealing ring, tighten the piston, overhaul the cylinder; check the pipeline and pipe joints, and deal with leakage in time.
Symptom 5: Drop bucket
When the loader is operating, the bucket reversing valve returns to the neutral position after the bucket is retracted, and the bucket will turn down and weigh the bucket. The reasons for dropping the bucket are: 1) The bucket selector valve is not in the neutral position, and the oil passage cannot be closed.
2) The seal of the bucket reversing valve is damaged, the gap between the valve core and the valve body hole is too large, and the leakage is large.
3) The bucket cylinder rodless cavity double-acting safety valve seal is damaged, jammed, and the overload pressure is too low. 4) The seal ring of the bucket hydraulic cylinder is damaged, severely worn, and the cylinder tube is strained.
Remedy: Clean the double-acting safety valve, replace the sealing ring, and adjust the overload pressure. For other troubleshooting methods, refer to Symptom 3.
Symptom 6: Oil temperature is too high
The main reasons for the high oil temperature are: the ambient temperature is too high and it works continuously for a long time; the system works under high pressure and the relief valve is frequently opened; the relief valve setting pressure is too high; there is friction inside the hydraulic pump; the hydraulic oil is not selected properly Or deterioration; insufficient oil. Check to determine the cause of the high oil temperature and eliminate it.
